Question

我目前正在课堂外从事个人项目，在将文本文件读入链表时遇到了一些问题。在第一本书中阅读时，我得到

java.lang.NumberFormatException: empty String

错误。我在程序中添加了一条打印行，以将要解析的内容打印为double值，变量实际上不是空值，实际上是double值。

就像我在上面说的那样，我添加了一条打印行以打印出我要解析为双精度的字符串，这似乎还可以。这是读入并拆分为我要从中打印的数组的字符串：

500.0 % 04/05/2019 % This is paycheck 1 % true % 49.5

我必须将两个字符串解析为双精度，而我只遇到第一个的问题。当我注释掉要解析的第一个double时，程序运行没有问题。这是从运行到程序的完整输出

 *File loading*


    *500.0*

    *Exception in thread "main" java.lang.NumberFormatException: empty String*
        *at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)*
        *at sun.misc.FloatingDecimal.parseDouble(Unknown Source)*
        *at java.lang.Double.parseDouble(Unknown Source)*
        *at fileHandling.readPaycheck(fileHandling.java:194)*
        *at UserMenu.main(UserMenu.java:20)*

此行代码中的“将数组拆分为适当的临时变量”部分中出现了问题：

payCheckAmount = Double.parseDouble(tempArray[0]);

这是此方法中的代码

public void readPaycheck(LinkedList<PayCheck> paycheck) throws IOException {

        // Declare Variables
        Scanner sc = new Scanner(payChecks); // Scanner used to read in from the payChecks text file
        String temp; // A string used to hold the data read in from the file temporarily
        String[] tempArray; // A String array used to temporarily hold data from the text file
        double payCheckAmount; // A double holding the amount of the paycheck
        String paycheckDate; // A string holding the date of the paycheck
        String description; // A string holding a description of the paycheck
        boolean payCheckSplit; // A boolean stating if the paycheck has been split or not
        double amountUnSplit; // A double

        // A while loop that runs while the text file still has data in it
        while (sc.hasNextLine()) {

            // Reading in a new line from the paycheck file
            temp = sc.nextLine();
            // Splitting the line into an array
            tempArray = temp.split(" % ");

            // Temp output used for testing of the issue at hand
            System.out.println(tempArray[0]);

            // Splitting the array into its appropriate temp variables
            payCheckAmount = Double.parseDouble(tempArray[0]);
            paycheckDate = tempArray[1];
            description = tempArray[2];
            payCheckSplit = Boolean.parseBoolean(tempArray[3]);
            amountUnSplit = Double.parseDouble(tempArray[4]);

            // putting the temp variables into a temp paycheck object
            PayCheck tempCheck = new PayCheck(payCheckAmount, paycheckDate, description, payCheckSplit, amountUnSplit);
            paycheck.add(tempCheck);

        }

    }

编辑：

这是我遇到的问题的最小，完整和可验证的示例：

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class test {

    public static void main(String[] args) throws IOException {

        // Declare Variables
        File payChecks = new File("C:\\Users\\zwtw\\Documents\\paychecks.txt");
        Scanner sc = new Scanner(payChecks); 

    while (sc.hasNextLine()) {

            String temp = sc.nextLine();

            String[] tempArray = temp.split(" % ");

            System.out.println(tempArray[0]);

            // Splitting the array into its appropriate temp variables
            double payCheckAmount = Double.parseDouble(tempArray[0]);
            String paycheckDate = tempArray[1];
            String description = tempArray[2];
            boolean payCheckSplit = Boolean.parseBoolean(tempArray[3]);
            double amountUnSplit = Double.parseDouble(tempArray[4]);

        }
    }
}

以下是上面代码中提到的文本文件的内容：

500.0 % 04/05/2019 % This is paycheck 1 % true % 49.5
450.0 % 04/09/2019 % This is paycheck 2 % true % 49.75

Answer 1

您的文本文件可能包含空行。您可以删除文本文件中的新行，更改文本文件的创建方式，或者在阅读时跳过空白行。

这是您跳过空白行的方法：

while (sc.hasNextLine()) {

        String temp = sc.nextLine();

        if (temp.equals("")) { continue; } // <--- notice this line
        String[] tempArray = temp.split(" % ");

        System.out.println(tempArray[0]);

        // Splitting the array into its appropriate temp variables
        double payCheckAmount = Double.parseDouble(tempArray[0]);
        String paycheckDate = tempArray[1];
        String description = tempArray[2];
        boolean payCheckSplit = Boolean.parseBoolean(tempArray[3]);
        double amountUnSplit = Double.parseDouble(tempArray[4]);

    }
}

“ java.lang.NumberFormatException：空字符串”，字符串不为空

1 个答案: